CVE-2026-6484 in H2O
Summary
by MITRE • 08/12/2026
In an UEFI, Lack of verified boot to certain FV may cause arbitrary code execution.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 08/12/2026
The vulnerability described represents a critical failure in the UEFI firmware security architecture where the system lacks proper verified boot mechanisms for specific firmware volumes. This weakness occurs when the firmware fails to validate the integrity and authenticity of firmware components stored in particular flash memory regions, creating an exploitable gap in the boot process that can be leveraged by malicious actors.
This flaw fundamentally undermines the chain of trust that UEFI implementations are designed to establish during system boot. The absence of verified boot for certain firmware volumes means that unauthorized code can be loaded and executed without proper cryptographic verification or integrity checks. According to the CWE catalog, this corresponds to CWE-1037 which describes insufficient verification of the authenticity of firmware components, and CWE-1105 which addresses inadequate protection against firmware tampering. The vulnerability allows for arbitrary code execution because the system cannot distinguish between legitimate firmware updates and malicious modifications.
The operational impact of this vulnerability is severe as it provides attackers with a persistent foothold in the system that operates below the operating system level. Once exploited, adversaries can install rootkits, modify boot processes, or establish backdoors that survive system reboots and OS reinstalls. This aligns with ATT&CK technique T1068 which covers local privilege escalation through bootkit installation, and T1542.003 which addresses boot or logon initialization scripts. The threat actor can leverage this weakness to maintain long-term access while evading traditional endpoint protection mechanisms that operate at the OS level.
Mitigation strategies must focus on implementing robust verified boot processes across all firmware volumes including proper cryptographic signing, integrity verification, and secure key management. Organizations should ensure that UEFI firmware is updated regularly with patches from vendors, implement hardware security modules for key storage, and configure firmware to enforce strict boot validation policies. The solution should also include monitoring for unauthorized firmware modifications and establishing secure supply chain practices to prevent pre-shipment tampering of firmware components.